Doctor fish is the name given to two species of fish: Garra rufa and Cyprinion macrostomus. Other nicknames include nibble fish, kangal fish, and doctorfishen; in non-medical contexts, Garra rufa is called the reddish log sucker. They live and breed in the outdoor pools of some Turkish spas, where they feed on the skin of patients with psoriasis. The fish are like combfishes in that they only consume the affected and dead areas of the skin, leaving the healthy skin to grow, with the outdoor location of the treatment bringing beneficial effects. The spas are not meant as a curative treatment option, only as a temporary alleviation of symptoms, and patients usually revisit the spas every few months. Some patients have experienced complete cure of psoriasis after repeated treatments, but due to the unpredictable nature of the disease, which is strongly influenced by endogenous factors, this may simply be regression towards the mean.

Garra rufa occurs in the river basins of the Northern and Central Middle East, mainly in Turkey, Syria, Iraq and Iran. It is legally protected from commercial exploitation in Turkey due to concerns of overharvesting for export. Garra rufa can be kept in an aquarium at home; while not strictly a "beginner's fish", it is quite hardy. For treatment of skin diseases, aquarium specimens are not well suited as the skin-feeding behavior fully manifests only under conditions where the food supply is somewhat scarce and unpredictable.

In 2006, doctor fish spa resorts opened in Hakone, Japan, and in Umag, Croatia, where the fish are used to clean the bathers at the spa. There are also spas in resorts in China, Belgium, the Netherlands, South Korea, Singapore, Hungary, Slovakia, India, Thailand, Indonesia, Malaysia, Philippines, Hong Kong, Bucharest, Romania, Barcelona, Spain and France. In 2008, the first widely known doctor fish pedicure service was opened in the United States in Alexandria, Virginia, and later in Woodbridge, Virginia. In 2010 the first UK spa opened in Sheffield. They are used to help treat patients suffering from various skin disorders, including psoriasis and eczema, since the fish will eat and remove any dead skin.